The induction of synthesis of vitellogenin by juvenile hormone in the fat body of the migratory locust, Locusta migratoria, is being investigated, as a model for analysis of the mechanism of action of a developmental hormone in regulating the synthesis of a specific protein. The juvenile hormone analog, methoprene (ZR-515) is chiefly used. The kinetics of stimulation of vitellogenin synthesis in adult female fat body will be studied in vivo and with tissue cultured in vitro. The development of competence to respond will be studied in female fat body, as well as the possibility of specific response in male fat body. The replication of DNA, and the synthesis of different kinds of RNA, in response to the hormone analog will be studied. Cytoplasmic and nuclear hormone receptors will be sought. DNA sequences representing the vitellogenin genes will be cloned from cDNA in the plasmid pBR322, and genomic clones will be selected from a locust DNA library in bacteriophage lambda. These will be used as hybrdization probes for assay of mRNA levels and gene frequency. Gene structure will be studied by restriction mapping and sequencing, with a view to discovering potentially regulatory sites.